TOXIC GASES AS A COI^TEOL OF THE PEACH-TREE BORER. 



13 



previously determined larvicidal value. The one-half-ounce dose in 

 many instances gave as perfect control as the next two larger doses, 

 and in some cases better. On the whole, however, the results from 

 the application of this dose are not quite so uniform and the general 

 average is slightly less. As will be seen from the table, there is not 

 a great difference in the control obtained from either the one-half- 

 ounce, the three- fourths-ounce, or the 1-ounce doses. Apparently 

 there is considerable latitude in the dosage required, within these 

 limits, but it does not seem likely that much less than one-half -ounce 

 doses would give consistent control. On the other hand, there does 

 not seem to be much point in using doses larger than 1 ounce. 



Other experiments were carried on in which very much larger 

 doses than those shown in Table VI were used, but in none of these 

 was there an advantage in the control obtained sufficient to offset the 

 probability of injury from the greatly prolonged fumigation. Table 

 IV gives the results of one such experiment, made at Springfield 

 in 1916. 



Table IV. — Effect of stated doses of para-dicMorotensene on 8-year-old peach 

 trees, Springfield, W. Va., 1916. 



Num- 



Dose per tree. 



Date of— 



Interval 

 in days 

 from ap- 

 plication 

 to exam- 

 ination. 



Number of active 

 larvse. 





ber of 

 trees. 



Applica- 

 tion. 



Examin- 

 ation. 



Total. 



Per 

 tree. 



Injury. 



5 





June 24 

 ...do 



Oct. 14 

 Oct. 27 

 Oct. 28 



...do 



Oct. 14 

 Oct. 18 

 Oct. 27 



...do 



Oct. 28 

 Oct. 14 

 Oct. 18 

 Oct. 28 

 Oct. 27 

 Oct. 28 

 Oct. 14 

 Oct. 27 

 Oct. 28 

 Oct. 27 

 Oct. 28 

 Oct. 14 

 Oct. 27 

 Oct. 28 



...do 



112 



125 



126 



67 



112 



116 



125 



125 



67 



112 



116 



126 



125 



67 



112 



125 



126 



125 



67 



112 



125 



126 



126 



67 



67 



67 



67 



29 

 12 

 3 



5.8 



2.4 



.6 





5 



do 





5 

 5 



do 



do 



...do 



Aug. 22 

 June 24 



...do 



...do 



.. do 



None. 



5 





9 

 25 

 15 



6 



1.8 

 5.0 

 3.0 

 1.2 





5 



5 

 5 



do 



do 



do 



None. 

 None. 



5 



.... do 



Aug. 22 

 June 24 

 ...do 





5 









None (1 tree moderate). 



5 



do 



3 



4 



.6 

 .8 



5 



5 



do 



do 



...do.... 

 ...do 



None. 



5 



. . . do 



Aug. 22 

 June 24 

 ...do 









5 











5 



do 









5 



. ..do 



do... 









5 



do 



...do 









5 



.. ..do 



Aug. 22 

 June 24 

 ...do 









5 





1 



None (1 tree severe). 



5 



do 





5 



do 



do 



do 



6ounces 



8ounces 



10 ounces 



...do.... 

 ...do 









5 









5 



Aug. 22 



...do 



...do.... 



....0.... 



...do.... 

 ...do.... 

 ...do.... 

 ...do.... 









2 







None (1 tree traces). 



2 







2 







None (1 tree traces). 









Total number of trees treated, 126. 



A total of 126 eight-year-old trees were treated with various doses, 

 ranging from one-half ounce to 10 ounces per tree. Part of the ap- 

 plications were made June 24 and part August 22. The examination 

 was made in October. Of the entire 126 trees, 66 which received 



